1. Field of the Invention
The present invention relates to a dust lip structure of an oil seal for an oscillation preferably employed for a hydraulic shock absorber or the like.
2. Description of the Related Art
In conventional art, in a dust lip structure of an oil seal for an oscillation, as described in Japanese Utility Model Application Laid-Open No. 6-28429, there is a structure having a dust lip in which a first dust lip portion in a front end side and a second dust lip portion in a base end side are in slidable contact with a rod with respective interferences. This oil seal is structured to reduce the thickness of a front end portion of the dust lip so as to prevent the first dust lip portion from being brought into close contact with the rod, increase a following property of the rod with respect to an axial eccentricity and increase a dust approach preventing effect.
However, in the conventional art, since the following property of the first dust lip portion with respect to the axial eccentricity of the rod is increased by reducing the thickness of the front end portion of the dust lip, a rigidity of the dust lip is reduced, and there is a possibility that the front end portion of the dust lip is drawn in the rod at a time of compressing the rod so as to be reversed. When the front end portion of the dust lip is reversed, a groove is generated in a contact portion between the rod and dust lip, and dusts, muddy water and the like are accumulated in the groove, thereby damaging the rod and further causing an oil leakage.
An object of the present invention is to prevent a dust lip from being reversed in an oil seal for oscillation.
The present invention relates to a dust lip structure of an oil seal for oscillation provided with a dust lip in which a first dust lip portion in a front end side and a second dust lip portion in a base end side are in slidable contact with a rod with respective interferences, in a core metal.
In one embodiment, a thickness of the front end portion of the dust lip is substantially two thirds of an interference of the first dust lip portion with respect to the rod. In another embodiment, this thickness is precisely two thirds.
An outer diameter of the dust lip is arranged to be parallel to each of a front end side taper-like inner diameter portion from the first dust lip portion to a root portion of the second dust lip portion and a base end side taper-like inner diameter portion from the second dust lip portion to the base end portion.